Re: [Full-Disclosure] Re; Time Expiry Algorithm

[Andrew Farmer <andfarm@xxxxxxxxxxxx>]

On 21 Nov 2004, at 00:14, Jacqueline Singh wrote:
> Gautam R. Singh <gautam.singh@xxxxxxxxx> wrote:
> > I was just wondering is there any encrytpion alogortim which expires
> > with time.
> > For example an email message maybe decrypted withing 48 hours of its
> > delivery otherwise it become usless or cant be decrypted with the
> > orignal key
>
> > > No. Think about it for a moment.
>
> > > (Clocks can be changed.)
>
> What if you decided to code into the encryption the use of atomic
> clocks, and include more than one or two as a redundancy/security
> check?

That's an implementation, not an algorithm.

An encryption *algorithm* must be a fixed set of rules that map inputs 
to outputs. In your proposed algorithm, one of the inputs is the 
current time - and that can be changed, by the *definition* of an 
algorithm.

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